bug#26891: 26.0.50; Error using lisp-indent-line in eval-expression minibuffer

[John Mastro]

Using lisp-indent-line in an eval-expression minibuffer (i.e. M-:) works
in Emacs 25 but causes a "Text is read-only" error in Emacs 26.

To reproduce:
1. Run emacs -Q
2. Evaluate the code below
3. Type M-:
4. Hit TAB

Here's the code:

    (defun init-eval-expression-minibuffer ()
      (setq-local indent-line-function #'lisp-indent-line)
      (local-set-key (kbd "TAB") #'indent-for-tab-command))

    (add-hook 'eval-expression-minibuffer-setup-hook
              #'init-eval-expression-minibuffer)

Point will move to the very beginning of the minibuffer (on the "E" in
"Eval") and you'll see a "Text is read only" message. (I called it an
error above but it doesn't actually invoke the debugger even with
debug-on-error and debug-on-signal non-nil).

It doesn't matter whether you have entered text or not before hitting
TAB.

Thanks,

John


In GNU Emacs 26.0.50 (build 4, x86_64-pc-linux-gnu, X toolkit, Xaw3d
scroll bars)
 of 2017-04-26 built on meta
Repository revision: 8f2062d96b0319fc2a837ba9e2c6b67abf31c920
System Description:     Fedora release 25 (Twenty Five)

Recent messages:
Loading /home/jbm/.emacs.d/defuns.el (source)...done
Loading /home/jbm/.emacs.d/local.el (source)...done
Loading /home/jbm/.emacs.d/custom.el (source)...done
Loading /home/jbm/.emacs.d/var/recentf...done
Cleaning up the recentf list...done (0 removed)
Loading /home/jbm/.emacs.d/var/company-statistics-cache.el (source)...done
Starting new Ispell process /usr/bin/aspell with default dictionary...

Configured using:
 'configure --with-xml2 --with-zlib --with-gnutls --with-x-toolkit=lucid
 --without-pop --without-compress-install'

Configured features:
XAW3D XPM JPEG TIFF GIF PNG SOUND NOTIFY GNUTLS LIBXML2 FREETYPE XFT
ZLIB TOOLKIT_SCROLL_BARS LUCID X11

Important settings:
  value of $LANG: en_US.UTF-8
  locale-coding-system: utf-8-unix

Major mode: Emacs-Lisp

Minor modes in effect:
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  flyspell-mode: t
  projectile-mode: t
  global-git-commit-mode: t
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  company-statistics-mode: t
  global-company-mode: t
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  ido-vertical-mode: t
  flx-ido-mode: t
  ido-ubiquitous-mode: t
  ido-everywhere: t
  smartparens-global-strict-mode: t
  paredit-mode: t
  global-undo-tree-mode: t
  undo-tree-mode: t
  winner-mode: t
  which-key-mode: t
  minibuffer-depth-indicate-mode: t
  recentf-mode: t
  whitespace-mode: t
  savehist-mode: t
  save-place-mode: t
  global-auto-revert-mode: t
  show-paren-mode: t
  global-hl-line-mode: t
  delete-selection-mode: t
  auto-compile-on-load-mode: t
  auto-compile-on-save-mode: t
  auto-compile-mode: t
  override-global-mode: t
  tooltip-mode: t
  global-eldoc-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  size-indication-mode: t
  column-number-mode: t
  line-number-mode: t
  auto-fill-function: do-auto-fill
  transient-mark-mode: t

Load-path shadows:
None found.

Features:
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mailheader pcvs-util add-log cl-indent hippie-exp comint ansi-color
company-statistics company smex ido-vertical-mode flx-ido ido-ubiquitous
cus-edit cus-start cus-load ido-completing-read+ ido ace-link avy
smartparens help-mode paredit undo-tree diff winner ring which-key
help-at-pt solarized-moar-theme solarized-theme solarized-definitions
mb-depth recentf tree-widget wid-edit whitespace savehist saveplace
autorevert filenotify time-date paren hl-line server cursor-sensor xclip
edmacro kmacro cc-engine cc-vars cc-defs ivy flx delsel ivy-overlay ffap
thingatpt subr-x pcase auto-compile packed use-package diminish bind-key
easy-mmode finder-inf gh-common gh-profile rx s marshal eieio-compat ht
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Memory information:
((conses 16 634597 116951)
 (symbols 48 42964 3)
 (miscs 40 77 204)
 (strings 32 97335 116596)
 (string-bytes 1 3181935)
 (vectors 16 86537)
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